As disclosed in Patent Document 1, there has been a conventional valve timing control device comprising a drive-side rotational member (corresponding to a “shoe housing” in Patent Document 1), a driven-side rotational member (corresponding to a “vane rotor” in Patent Document 1), a fluid pressure chamber (corresponding to a “storing chamber” in Patent Document 1) defined by the drive-side rotational member and the driven-side rotational member, a partition (corresponding to a “vane” in Patent Document 1) provided in the driven-side rotational member for dividing the fluid pressure chamber into the retarded angle chamber and the advanced angle chamber, a fluid control mechanism (corresponding to an “oil pump”, “switching valve” and “drain” in Patent Document 1) for controlling feed/discharge of the working fluid relative to the fluid pressure chamber, and a locking mechanism (corresponding to a “restricting member” in Patent Document 1) for restricting the relative rotational phase of the driven-side rotational member relative to the drive-side rotational member to the predetermined phase between the most retarded angle phase and the most advanced angle phase.
According to the invention disclosed in Patent Document 1, the relative rotational phase can be reliably set to an optimum initial phase when the engine is started based on the operation of the locking mechanism. Thus, the intake timing and the ignition timing of the engine are optimized to provide a low-emission engine with reduced harmful combustion emissions, e.g., hydrocarbon (HC).
Further, while the engine is driving, a displacement force applied in the retarded angle direction and a displacement force applied in the advanced angle direction based on torque variations of the camshaft are usually exerted to the driven-side rotational member. The displacement force is exerted in the retarded angle direction on average, which causes the driven-side rotational member to displace in the retarded angle direction. Hereinafter, the average of both the displacement force applied in the retarded angle direction and the displacement force applied in the advanced angle direction based on the torque variations of the camshaft will be referred to as an “average displacement force applied in the retarded angle direction based on the torque variations of the camshaft.” The valve timing control device disclosed in Patent Document 1 is provided with an advanced angle member for adding torque to the driven-side rotational member in the advanced angle direction, thereby to allow the relative rotational phase to displace smoothly and quickly in the advanced angle direction regardless of the average displacement force applied in the retarded angle direction based on the torque variations of the camshaft.